/Engine/Source/Editor/UnrealEd/Public/EditorLevelUtils.h
Sets the actors within a level's visibility via bHiddenEdLevel. Warning: modifiesULevel::bIsVisibleand bHiddenEdLevel without marking packages dirty or supporting undo. Calling code must restore to the original state before the user can interact with the levels.
static void SetLevelVisibilityTemporarily ( [ULevel](API\Runtime\Engine\Engine\ULevel) * Level, bool bShouldBeVisible )